Method of lubricating vitreous fibres



United States Patent 3,297,470 METHOD OF LUBRICATING VITREOUS FIBRES Richard A. Martel, Sylmar, Calif., assignor to General Precision, Inc., a corporation of Delaware No Drawing. Continuation of application Ser. No. 215,784, Aug. 9, 1962. This application Oct. 13, E65, Ser. No. 495,714

1 Claim. (Cl. 11754) This is a continuation of United States patent application, Serial Number 215,784, filed August 9, 1962 and now abandoned.

The present invention relates to vitreous fibres, such as fibres made from quartz or glass. For yarn or cloth made from such fibres to have adequate tensile strength, it is necessary that the fibres be lubricated so that they may move smoothly relatively to each other when the yarn or cloth is flexed; otherwise the fibres break in a very short period of time and the yarn or cloth made therefrom disintegrates. For this reason vitreous fibres are now usually impregnated with oils, such as starch oil.

Vitreous materials are inherently heat-resistant as compared with other fibre materials, and vitreous fibres are therefore potentially most useful in fields of application wherein they are subjected to high temperatures. The lubricants now commonly in use on vitreous fibres, however, break down quickly at high temperatures and yarn or fabrics made from such fibres lose their tensile strength and disintegrate in a very short period of time when subjected to temperatures of the order of 1000 F.

It is an object of my invention to provide vitreous yarn or cloth that has improved tensile strength at high temperatures.

Another object of the invention is to provide vitreous fibres with a lubrication that remains effective at high temperatures.

1 have found that powdered boron nitride when applied to vitreous fibres, performs extremely well as a lubricant and remains effective at high temperatures so that yarn or cloth made from fibres provided with a boron nitride coat may be employed at temperatures in excess of 1000 F. without appreciable deterioration of its tensile strength. It is, however, not a simple matter to provide the fibres of vitreous yarn or cloth with an adequate and uniform coat of boron nitride that will dependably adhere to the fibres and thus preserve the tensile strength of yarn and cloth made from such fibres at high temperatures.

It is another object of my invention, therefore, to provide an effective method of applying a dry lubricant, such as boron nitride, to vitreous fibres.

Still another object of the invention is to provide a method of applying a dry, powdered lubricant to vitreous fibres in such a manner that it adheres dependably to the fibres at high temperatures.

These and other objects of the invention will be apparent from the following description of a preferred embodiment thereof.

I have found that a uniform and firmly adhering coat of a dry, powdered lubricant may be applied to vitreous fibres by subjecting them to ultrasonic vibration in a fiuid medium that has a high dielectric constant, and then immersing the fibres in a suspension of the powdered lubricant in a fluid medium of a low dielectric constant.

In carrying out the invention in practice, I applied a coat of powdered boron nitride to a yarn made of quartz fibres. Since commonly available quartz fibre yarns are now generally provided with starch oil lubrication, it Was first necessary to remove the coat of starch oil from the ice fibres. For this purpose the yarn was washed in a bath of water containing a suitable detergent, for instance, a detergent of the alkyl aryl sulfonate type. The cleaned yarn was then placed into a container of clear water that was immersed in a tank of water that was ultrasonically vibrated. Satisfactory results were obtained by subjecting the fibres in the water bath to a vibration of 60 kilocycles for about one minute. Clear water has a dielectric constant of about 80, and as a result thereof the vibrations to which the yarn was subjected, built up a significant electric charge upon the fibres. To dry the yarn, it was then immersed into a beaker of acetone, that was likewise subjected to vibrations of about 60 kc. in a vibratory tank. Acetone has a dielectric constant of only about 40, and as a result thereof each fibre lost some of its electric charge, but the charge retained upon the fibres was still large enough to operate in the spirit of the invention. Upon removal from the acetone, .and evaporation of the residual acetone on the fibres, the fibres were thoroughly dry. The yarn was now immersed in a beaker containing a suspension of boron nitride powder in normal heptane. The boron nitride powder was of a fineness passing through a 325 mesh screen. Normal heptane is nearly non-polar; it has a dielectric constant of only about 2. The beaker containing the suspension of boron nitride in heptane was likewise vibrated in a vibratory tank at a frequency of about 60 kilocycles to maintain the boron nitride in suspension. The particles of boron nitride were immediately attracted to the quartz fibres and formed a thin uniform coat thereon that adhered tenaciously to the fibres after they were removed from the suspension. It was only necessary to leave the yarn in the suspension for approximately 20 seconds.

The yarn treated as described above retained of its tensile strength when subjected to temperatures up to 1500 F. for fifteen minutes, whereas vitreous fibres lubricated with conventional methods lose of their tensile strength and deteriorate in less than 15 minutes at temperatures of 1000 F.

While I do not know for certain why the described method of applying a coat of powdered boron nitride to fibres produces such a uniform and firmly adhering coat upon the fibres, I believe that vibration of the fibres in a fluid medium of a high dielectric constant builds up electric charges upon the fibres, as I have previously pointed out. A portion, or perhaps all, of the boron nitride particles in the suspension of heptane apparently have electric charges of opposite polarity, and when the charged quartz fibres are immersed into the suspension of boron nitride particles in a low dielectric medium, they attract immediately the oppositely charged particles of boron nitride, and thereafter the vitreous fibres and the boron nitride particles adhere to each other and form a firm and tenacious union.

Whatever the scientific explanation may be, a dependable and uniform coat of boron nitride is formed in the described manner on vitreous fibres, and the fibres thus coated are capable of forming yarn and cloth that remain intact and retain superior tensile strength even when subjected to temperatures of the order of 1000 F., and up to 1500 F., for significant periods of time.

While I have explained my invention with the aid of a particular embodiment thereof, it will be understood that the invention is not limited to the specific substances, the times of treatment and the frequency of vibrations given by way of example, which may be departed from without departing from the scope and spirit of the invention.

3 4 I claim: immersing the vitreous fibres in a bath of normal hep- A method of adhering boron nitride to vitreous fibres mm which s a dielectric cons nt Of about 2 and which has a suspension of boron nitride therein; and

comprising the steps:

ultrasonically vibrating the bath of normal heptane at immersing the vitreous fibers in a bath of Water having a dielectric constant of about 80; 5 about 60 ultrasonically vibrating the fibres at about 60 kc.; References Cited by the Examiner removing the vitreous fibres from the bath of Water UNITED STATES PATENTS and immerslng the vitreous fibres m a bath of ace- 455,187 6/1891 Erlweim 10 2,491,761 12/1949 Parker et al 106-50 X ultrasonically vibrating the vitreous fibres 1n the bath 2,748,030 5/1956 Silversher et aL of acetone at about 60 kc.; removing the vitreous fibres from the bath of acetone ALFRED LEAVITT Pnmary Exammer' and allowing the residue of acetone to evaporate; W. L. SOFFIAN, Assistant Examiner. 

